Without limiting the scope of the invention, its background is described in connection with video camera units and video adapters. Although, video adapters for generic video cameras have been in use for years in an attempt to enhance the quality of the recorded image and reduce the optical depth of field to create a more desirable film-like image, they are typically complex, expensive and do not provide cinematic quality depth of field control. The inability to use interchangeable 35 mm lenses has left the depth-of-field (DOF) problem elusive or too expensive to achieve. The image sensors in most video cameras are too small to provide cinematic depth of field control. It is very difficult to get an object in sharp focus in the foreground against a blurred background, to communicate depth with focus, and to provide cinematic rack focus for shifting attention in a scene with most video cameras.
More specifically, conventional video camera adapters are expensive and require many individual components to achieve the desired effect. Moreover, each component adds cost and must be carefully selected and matched to meet the requirements of the overall system. In addition, these conventional multi-function imaging elements negatively affect image quality. For example, a separate DCX or Fresnel lens glued to the focusing screen; however, this approach degrades the image by reducing overall resolution and contrast of the projected image. Also, another problem is long-term loss of optical quality as many adapters do not incorporate a UV filter and suffer from degrading image quality over time due to damage from UV light.
For example, U.S. patent application Ser. No. 10/469,295 entitled “Video Camera and Adapter for said Video Camera” discloses a video camera. The adapter has a camera housing with a first objective, through which light from a scene to be picked up is guidable into the camera housing. A semiconductor sensor field, on which light from the scene to be picked up is able to be cumulated. The device further includes a projection area disposed with respect to the first objective such that light introduced through the first objective is imaged onto the projection area. A second objective disposed with respect to the projection area and to the semiconductor sensor field such that light from the projection area is imaged onto the semiconductor sensor field.
Similarly, U.S. patent application Ser. No. 10/877,371 entitled “Video-Camera Unit and Adapter for a Video-Camera Unit” discloses an adapter for a video camera. The adapter has a connection for a camera lens, a connection for a video camera, and an image transfer unit disposed between these two connections. The image transfer unit has a photoreceptive surface and wherein the image transfer unit further includes a beam splitter for branching off an optical viewfinder path. An optical deflection element can be moved into and out of the optical viewfinder path so that the optical viewfinder image or the image of a monitor can be seen by a user.
While these devices may be suitable for the particular purpose to which they address, they are less desirable for creating the look of 35 mm film with a more shallow focus using a video camera unit.